A1c to eAG (Estimated Average Glucose) Calculator

Convert HbA1c (%) to estimated average glucose: eAG (mg/dL) = 28.7 × A1c − 46.7. ADAG / Nathan 2008.

Inputs

DCCT/NGSP standardized %.

Result

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How to use this calculator

  • Enter HbA1c (%).
  • Choose output units (mg/dL US default, mmol/L international).
  • Compare eAG to your fingerstick log average — should be within 30 mg/dL.

About this calculator

eAG (estimated average glucose) translates HbA1c into the same units as a fingerstick reading. Linear regression from the ADAG (A1C-Derived Average Glucose) Study (Nathan et al., Diabetes Care 2008;31:1473) across 507 subjects with T1DM, T2DM, or no diabetes. Formula: eAG (mg/dL) = 28.7 × A1c − 46.7. ADA categories: <5.7% non-diabetic, 5.7-6.4% pre-diabetes, ≥6.5% diabetes. Source: American Diabetes Association Standards of Care 2026 (annual update); Nathan DM et al. "Translating the A1C Assay Into Estimated Average Glucose Values" Diabetes Care 2008. **Not medical advice — use clinical context and labs, not a single number.**

Frequently asked

Source of the formula?+
Nathan DM et al., Diabetes Care 2008;31(8):1473-78. The ADAG Study correlated A1c with continuous glucose monitoring across 507 subjects of mixed diabetes types.
Why does eAG differ from my fingerstick average?+
A1c reflects the prior 8-12 weeks weighted to the most recent 4 weeks. Fingersticks miss overnight + post-meal peaks. Use CGM (continuous glucose monitor) for closer agreement.
A1c units (NGSP vs IFCC)?+
US/UK use NGSP (%). IFCC uses mmol/mol. Conversion: NGSP% = (IFCC mmol/mol × 0.0915) + 2.15. This calc uses NGSP %.
Limits of A1c?+
Inaccurate in iron deficiency anemia, hemoglobinopathies (SS, SC, β-thal), recent transfusion, kidney failure on EPO. Use fructosamine or glycated albumin in those cases.
ADA target A1c?+
Generally <7% for most adults; <6.5% if achievable safely; <8% in elderly with comorbidities. Individualize. Source: ADA Standards of Care 2026.
Is this medical advice?+
No. Educational tool only. Clinical decisions require labs, history, and a clinician.

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